P0430 Nissan 3.5L – Testing the Catalytic Converter

This P0430 Nissan OBDII trouble code refers to the emissions system in your 1995+ OBDII vehicle. The specific term for this check engine code is Catalyst System Efficiency Below Threshold. That means there is damage or something causing an excess fuel condition in the downstream oxygen sensor, which indicates a catalytic converter failure.

Today I’ll be showing you how to test this in a 2006 Nissan 350Z with the VQ35DE engine. This Nissan code is for Bank 2 which is the left side of the motor, if you are testing a front wheel drive version of this engine, Bank 2 is the side near the radiator or the front of your car. The testing methods are the same no matter what version of this VQ you own, but keep in mind that Bank 1 represents the side Cylinder 1 is, in case you get confused.

In closed loop operation the Engine Control Unit (ECU) monitors the air fuel ratio for the switching frequency in both the upstream and downstream 02 sensors. When your Nissan three way exhaust catalyst loses oxygen storage capacity or fails prematurely, the downstream oxygen sensor switching frequency will rise triggering the check engine code P0430 Nissan or P0420.

Possible causes of P0430 Catalyst System Efficiency Below Threshold

  • Failure of three way catalytic converter
  • Exhaust leaks
  • Faulty fuel injector
  • Faulty spark plug
  • Incorrect base ignition timing
  • Modified fuel system

The P0430 Nissan and P0420 check engine code is indicated by the MIL lamp or Malfunction Indicator Lamp being turned on. I will be showing you how to test the catalyst and test the downstream 02 sensor as well.

How to test at the ECU


Before you can learn what the problem in your Nissan is, you’ve got to find out what the ECU is seeing from the downstream oxygen sensors. To perform this basic test, you will need to gain access to your ECU, which is located behind the passenger side footpanel.

In order to access your Nissan 350Z ECU, remove the cup holder and pull off the door panel located on the floor. There’s a screw that secures the corner of the footwell, and once you remove this you can pull off the panel to expose your ECU.

  1. Start your Nissan vehicle
  2. Once it warms up, turn off the engine and ignition
  3. After waiting 10 seconds start engine again
  4. Hold RPM from 3,500 RPM to 4,000 RPM for at least 1 minute. Do not put car into gear.
  5. Allow engine to idle and open hood.


Keep in mind that this test will only allow you to read the output of your secondary oxygen sensor by referencing your ECU directly. If you find that your oxygen sensor voltage is low or your 02 sensor is responding lazily, you will need to replace and service your catalytic converter.

Where is my Nissan ECU?

The ECU is located on the passenger side of the dash, and mounted under the glove compartment. There is a plastic shield that holds the undertray of the ECU, simply flip this tray down to access the ECU cover and the wiring harness.


Here are the steps to test your oxygen sensor input directly at your 3.5 liter Nissan ECU.

  1. Identify which oxygen sensor is having the issue.
  2. Measure the signal for the corresponding oxygen sensor ( If your front 02 sensor is reporting the issue, use PIN 74. If the secondary or downstream oxygen sensor is the culprit, turn to PIN 55.
  3. While measuring this wire by way of backpinned ECU wire, you must monitor for voltage fluctuation.
  4. Start the engine
  5. Allow engine to warm up
  6. Rev and hold engine speed at 2500 RPM

What you are looking for is the cycling that represents closed loop operation. Holding your RPM steady at 2500 RPM, you must check the oxygen sensor in question and watch for fluctuations. If your catalytic converter is working correctly, your secondary oxygen sensor will begin to cycle after 10 seconds.

If your downstream 02 sensor fails to cycle or change after this time, your catalytic converter or Nissan cat may have failed. According to Nissan, the complete oxygen sensor cycle for this 3.5 liter engine is 0.6 – 1.0 – 0 – 0.3 – 0.6 – 1.0.

Find that your 02 sensor isn’t responding or cycling like you want it? Replace your catalytic converter and clear your P0430 Nissan trouble code, if you have any questions please let me know below.

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